Semiconductor integrated circuit (IC) technology can be used to form microelectromechanical (MEM) devices, including optical modulators or switchable mirrors (i.e. optical beam deflectors) as disclosed in exemplary U.S. Pat. Nos. 5,212,582; 5,311,360 and 5,579,151. Conventional MEM optical modulators or switchable mirrors rely on stops that limit a range of movement of the mirror to prevent short circuiting of the MEM device. Mechanical contact between the mirrors and the stops, however, can result in stiction due to van der Waals forces or surface contamination. Stiction limits device reliability and requires the use of a reset voltage sequence to allow the mirror to change states. Anti-stiction coatings have also been developed in an attempt to alleviate stiction, but long-term reliability remains a problem whenever two micromachined surfaces come into contact. Thus, there is a need for improved MEM devices that overcome the problem of stiction and thereby provide an increased reliability.
An advantage of the present invention is that a bistable MEM actuator is provided with a moveable membrane shaped to preclude, in some preferred embodiments of the present invention, any contact between the membrane and an underlying substrate electrode or stop, thereby eliminating stiction.
A further advantage of the present invention is that the bistable MEM actuator can be adapted to form many different types of MEM devices, including mechanical memories, optical modulators, optical beam deflectors (i.e. switchable or rotatable mirrors) and latching relays.
Yet another advantage of the present invention is that the bistable MEM actuator remains stable in a quiescent state after the removal of electrical power (i.e. a programming voltage) from the device, thereby simplifying operation of the device, improving device reliability, and providing for nonvolatile operation of the device.
These and other advantages of the apparatus of the present invention will become evident to those skilled in the art.